Unexpected
by The Weatherwitch
Summary: Sirius Black meets muggle Isla in a bar, what happens next could change the world. AU, SB/OC, FW/OC Rated M for language and mature themes and scenes.
1. Chapter 1

Sirius Black, James Potter, Remus Lupin, and Peter Pettigrew all pilled in to what purported to be a rock club in the city of Edinburgh. It was James Potter's stag do, a name they found hilarious for obvious reasons. Sirius had acquired a pair of reindeer antlers, like the ones found in shops near Christmas time, and used a sticking charm to keep them on James's head. If they hadn't been in a muggle area, Sirius would have insisted James use his own animagus antlers. This wasn't their first pub of the night, or even their first city, but muggle booze had nothing on firewhiskey, so they were still only slightly tiddly. They ordered drinks from the bar, joking and laughing with each other, but stopped when the music died and an announcer began to speak.

"And now, ladies and gentlemen! We have a special treat for you tonight! A burlesque performance by the Sirens!"

The Marauders shared glances, "Nice choice Padfoot! Strippers without going to a strip club!" Peter crowed, the others laughed.

"Actually," a voice from behind them interrupted "Burlesque is not the same as stripping, there's a bit more artistry, often a comedic element, and you don't see nipples or bare crotch." The bartender continued pulling the pint he was working on, but glared slightly at Peter. Peter looked sheepish, and the others shared looks before turning towards the small stage with interest.

Fat Bottom Girls by Queen, a song that had come out the year before had started to play, and there were 3 women on stage wearing leather jackets, suspenders, and tiny flowy miniskirts. Sirius couldn't tear his eyes from the beautifully swaying behinds on stage, they moved perfectly in time with the music, with their tiny skirts emphasising their every movement. The one in the middle made eye contact with him across the room as she seductively dragged her hands up her leg, and he was pretty sure he drooled when they removed their leather jackets and shimmied their fringed bra clad breasts at the crowd, the one in the middle winking at him this time. People whistled and cheered when the skirts came off, and the dancers wiggled their bums at the crowd as the song came to a close. Just as the bartender had said, the important bits were still covered by the end, and Sirius was pretty sure he'd seen women wearing smaller bikinis, but it was still damn sexy.

All thoughts of bar hopping again left their minds, and they watched another two performances with fixated interest. The performances finished and they whooped and cheered with the rest of the crowd, before Sirius declared he was going out for a cigarette.

Sirius stepped outside and down a small alley before pulling out a cigarette and lighting it with his want surreptitiously, he took a deep drag and sighed in contentment. The night was going well, even if they weren't really drunk enough yet for his liking, it was a stag do after all! A door opened a little bit down the alley, and a young woman came tripping out, dropped something, and let out an impressive string of swear words.

"Fucking shit bugger fucking bollocks! Of course, of fucking course! Argh!" she yelled to the sky, before turning around and smacking her forehead on the door she had just walked out of.

"Uhh are you ok?" Sirius asked, unsure and only slightly amused. Her head whipped up, and he found himself looking into the eyes of the girl who'd winked at him from the stage.

"Are you serious?" she asked in a disparaging tone of voice, raising an eyebrow.

He couldn't help it, he grinned and said "Yes actually, how did you guess? Sirius Black, at your service." He gave an elaborate bow, and she snorted and cracked a small smile.

"Your parents named you Sirius? You poor thing." She let out another small laugh and walked closer to him.

"Eh, I don't mind, it's given me a _Sirius_ appreciation for puns." He winked and she laughed again "But seriously, what's up? Can I help at all?"

She sighed.

"Everything is up, but if I could nab a cigarette off you that would improve things a wee bit. I just dropped mine in that puddle back there." She jerked her thumb back to the door she'd come out of and he saw an open pack of cigarettes that was now completely soaked. He handed her a cigarette and helped her light it using the end of his, before getting himself another.

"Better?" he asked, as she took a deep drag and let it out in a long breath, eyes closed and leaning against the wall. She nodded and smiled up at him, before her face took on a curious expression. She pursed her lips and looked him up and down, he smirked and raised an eyebrow at her.

"Like what you see?" He asked.

"Not as much as you did!" she laughed. _Damn, she saw me staring_ he thought.

"I have a proposition for you, if you really want to help me?" she tilted her head to one side and looked at him from under her lashes.

"Go on." He said.

"One of the reasons I came storming out here in a huff, is that my arse of an ex-boyfriend is here. I don't know why, I don't know what his motives are, but he was a manipulative son of a bitch and it's entirely possible he's just here to make me have this freak out." She took another long drag on the cigarette. "Can you like, pretend that you fancy me or something? I'm really not in the mood for that confrontation tonight and" her eyes traversed his six foot, broad shouldered frame "you might be just the thing I need to keep him away."

"Oh princess, I'm not going to have to pretend anything at all." He said with a suggestive smirk, eyeing her tiny leather shorts, suspenders, and slightly baggy leather jacket. She laughed.

"Come on then lover boy, the other girls will be down in a bit, let me buy you a drink." She grabbed his hand and lightly pulled him back to the front entrance of the club. She gave the bouncer a wave and they headed back inside. The mouths of James, Remus, and Peter all dropped when they saw him being lead back inside by none other than the blue haired beauty from the stage, he couldn't help but smirk a little. She bought a double vodka coke for herself, and a double jack and coke for him, having a brief word with the bartender who had spoken the Marauders earlier as she did so.

"So do you do this all the time?" he asked "The dancing I mean, not the guilt tripping random men into hanging out with you." He teased. She raised an eyebrow, _she does that a lot_ he mused.

"Guilt tripping you am I? So I didn't see you staring at me while I was dancing? Or wiping that wee bit of drool off your chin?" She teased right back, with mock indignation.

"She has you there pads!" James laughed, as the other marauders came over.

"Pads?" She asked with a confused look at him.

"Shortened old school nickname." He explained. "This is James Potter, Remus Lupin, and Peter Pettigrew," he introduced the other Marauders, "Guys this is… actually, I didn't even ask your name!" he smacked himself in the forehead and she laughed. _She also does that a lot,_ he thought.

"Nice to meet you guys, I'm Isla, and to answer your previous question Sirius, we do this sort of thing every few months or so. It's the Fringe festival at the moment so there's all sorts of performances and things on at the moment." She turned to James, "Nice antlers, stag do?" she asked with a smirk and a twinkle of amusement in her eyes.

"Aha! Told you somebody would get it!" Sirius exclaimed, as Peter and Remus cracked up. James pulled on the antlers, but being in a muggle area, he couldn't use his wand to undo Sirius's sneaky sticking charm. "I knew there was a reason I liked you." He grinned and put his arm around Sorcha's shoulders.

"Your idea?" she giggled, looking at Sirius. He nodded proudly, puffing out his chest. "You really do have a _sirius_ appreciation for puns." She remarked with a smirk.

The night continued to be full of drinking, dancing, and laughter. Isla's dancer friends joined the group, along with a few others, and soon it seemed they knew half the bar.

The next time Isla and Sirius went out for a cigarette, he pulled her back into the alley they had met in and snogged the living daylights out of her. Her hands gripped his shoulders, and he had one arm round her waist, the other hand tangled in her wildly curly hair.

When they went back inside, she made eye contact with her ex, who was staring at her with a furious expression, and smirked. She had a quiet conversation with her friends, before going back to Sirius and whispering in his ear,

"I have a bottle of dark rum and an empty flat for the next three hours or so, are you coming?" She started walking away, and smirked when Sirius caught up with her before she got half way across the bar.

He pushed her against the wall the second they got in her flat, she groaned in pleasure and tugged his leather jacket from his shoulders. She manoeuvred them into her bedroom and shoved him down onto her double bed, grinning at the shocked look on his face. He sat up and made to grab for her and pull her down with him, but she skipped away.

"Ah ah ah," she said, "hands down." He complied, and she bent down to remove the Doc Martens she wore on her feet. He discretely removed the wand holster from his forearm and put that and his jacket on the floor. She prowled towards him and kissed him possessively, before pushing him down again and straddling him. She began to tug his t-shirt up, moving painfully slowly. He fisted his hands in the covers, she wanted to play this game, so he might as well enjoy it. She removed his t-shirt from him and began to kiss her way down his body, he groaned when she grazed a nipple with her teeth, and bit his lip as she began to work on the belt buckle of his leather trousers. He didn't think he could grip the covers any tighter, but when she took the head in her mouth he couldn't help but clench his fists in the covers even more and let out a tortured "Fuck yesssssss." After what felt like hours of sweet, sweet torture she crawled back up his body and he saw her sexy evil smirk.

"Hands above your head." She ordered, and he obeyed without question.

That wasn't the last time they had sex that night, and when Sirius crept out early the next morning trying not to wake the soundly sleeping Isla in his rush to get to his best mate's wedding, he completely intended on coming back.

Unfortunately, fate had other plans.

 **AN: So, I'm writing again after having a massive identity crisis and deleting everything I've ever done. Hope you enjoy, this is really just a bit of fun while I ease myself back into this thing.**

 **For those who are unsure, Isla is pronounced eye-la**


	2. Chapter 2

19 year old Isla O'Burn stared at the pregnancy test. It was positive. Fuck. Why was she always so forgetful and irresponsible? Fuck. Fuckity fuck fuck. What was she going to do? She hadn't heard from Sirius after he fucked off into the night, without even leaving a note, and had no idea how to go about finding him to tell him. Did she even want to tell him? What was she going to do about uni? There was no way she could afford to stay in her flat _and_ have a baby. Fuck. There was only one thing for it, she had to go to her parents. They lived in Musselburgh, on the outskirts of Edinburgh, she should still be able to go to classes and stuff if she ended up going home. _If they don't hate me._

Isla stood in her childhood bedroom, now equipped with baby crib, and tried not to cry. This is _so_ not how she pictured her life turning out. She rubbed her slightly swollen belly absentmindedly. At least her parents were trying to be supportive, although she wasn't entirely sure her father would ever truly forgive her.

She waddled out of her Shakespeare's Comedies seminar, or at least she felt like she was waddling. She was stressing out. She had about 9 weeks to go, and her last exam for this year was in just over 6 weeks.

She actually cried with relief when she left her final exam. Stupid pregnancy hormones. She really was waddling now as she looked for somewhere she could sit down and compose herself. She'd made it. She was done for the year, and she was taking a year out to have the baby and get used to having a child who depended on her. She was determined she was still going to get her degree, she had to.

 _Fuck you Sirius Black. Fuck you Sirius Black. Fuck you Sirius Black_. This was her mental mantra throughout her labour. She was doubting now that that was even his real name, but it was the name she knew him as, so that's what she called him. Eilidh Rose O'burn came into the world in a lightening quick 2 hours and 24 minutes, screaming her head off, with a mop of black curls.

She was a good baby, _thank fuck,_ Isla thought. She loved being held and would happily go to anyone. She was quickly able to latch on and suckle, and hardly ever fussed, though that could have been partly to do with the fact that Isla hardly ever put her down. She was fascinated, nervous and completely in love all at once. She was determined that Eilidh would never feel like she was missing out by not having a father.

Isla stood in her graduation gown, grinning ear to ear. She had done it. Now she just had to do her Postgraduate teacher training. _Fuck you Sirius Black._

The first time she noticed something odd happen, was when a dress Eilidh received as a present from one of Isla's aunts which Isla could have _sworn_ was pink, somehow ended up red. She chalked it up to a bad memory and a busy week, and shrugged it off.

The day she finally qualified as a teacher of English and Drama was one of the proudest of her life. Eilidh was a cheerful, smart and beautiful nearly five year old, but fuck did she look like her father with that dark hair and stormy grey eyes. _Fuck you Sirius Black._

The second time something slightly odd had happened around her daughter, was when she came home to find that five year old Eilidh had been sent home from school for fighting. Luckily, Isla's little brother who had only just started University was skiving that day, and was able to pick up the home phone and then pick up little Eilidh. A boy at school had been teasing her, and she'd somehow managed to push him over five feet away from her.

The day she got the keys to her very own little three bedroom house in Musselburgh was another one of the proudest moments of her life. The now six year old Eilidh ran around the house, looking in every crevice, and Isla let out a contented sigh.

When Eilidh turned seven, Isla started doing the odd burlesque night again, she'd heard 'Pour Some Sugar on Me' by Def Leppard and couldn't help herself. It was amazing to feel sexy again, and she was only 27 for fuck's sake! Obviously only on weekends and when Eilidh could stay with her grandparents though.

Eilidh continued to be far too bright and mischievous for her own good, or Isla's good for that matter! She was constantly asking questions, interested in _everything_ , and an independent streak a mile wide. Eilidh was a dog person through and through, with seemingly boundless energy, and she nearly cried with joy and excitement when Isla announced that they were going to pick a dog from the shelter for Eilidh's eighth birthday. Eilidh picked out a very sad looking brown and white Staffie, and named him Ozzy. He followed her everywhere and loved nothing more than to snuggle up with her, or roll around together like a pair of loons in their smallish back garden.

When Minerva McGonagall came to explain about Hogwarts and the wizarding world, she kicked herself for simply brushing off the odd things that had happened every couple of years around Eilidh, it made so much sense now! Of course, she was absolutely thrilled that her daughter was a witch, how cool was that?! She had to admit, she was a _tiny_ bit jealous of her daughter's apparent ability.

Diagon Alley was simply _awesome_! She bought a whole bunch more books on the magical world to read for herself, along with Eilidh's school books, although she did have to have a lie down in a dark room after thinking about the amount of money she'd spent in one afternoon. She had, however, also discovered that there were _wizard_ newspapers and magazines! If her daughter was going to be a part of this world, she would bloody well be informed about it. Isla took out subscriptions for both her and Eilidh (seeing as Eilidh would be away at Hogwarts for most of the year) from the Daily Prophet, the Quibbler, and Witch Weekly.

Sending Eilidh off on the Hogwarts express was a bittersweet moment. They'd come down to London the day before, and had a proper Mum and Daughter day before waking up that morning for Eilidh's send off. She was so proud and excited for her daughter. But she was now properly alone until December, for the first time in more than eleven years. Isla headed for her own platform for the train back up to Edinburgh, and had a wee cry to herself once she found her allotted seat. At least today was a Sunday and she had time to pull herself together before going back to teaching the next day.

Ozzy howled for a week straight, and refused to sleep anywhere except Eilidh's empty bed.

Her first piece of owl post arrived while she was at work on Monday.

 _Dear Mum,_

 _I'm a Gryffindor! It's the house of the brave apparently, our symbol is a Lion! It's so cool here! There are these four massive house tables in the Great Hall, and the food just appears out of nowhere! And the ceiling looks like it isn't there! And there are hundreds of these floating candles above the table, but the wax never drips on you for some reason._

 _Ooh! Apparently there was this big war thing a few years ago, and this boy in my year called Harry Potter killed the baddie when he was only a baby!_

 _The Headmaster looks like Merlin or Gandalf or something, he has long white hair and a long white beard and wears very bright clothes and pointy hats all the time apparently._

 _There are so many cool and weird things here Mum! I wish you could see it!_

 _Missing you already._

 _Lots of love,_

 _Eilidh_

 _Xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx_

 _P.S. THERE ARE GHOSTS HER, HOW COOL/WEIRD/CREEPY IS THAT?!_

Isla laughed when she read the letter, although she was slightly concerned that nobody had mentioned a recent war to her in the 'welcome to the wizarding world' speech. She wrote back to congratulate her daughter, and to agree that ghost being in the school was cool, weird _and_ creepy. She did however express her doubts that a head teacher would look that strange, even if this was the wizarding world.

She received a letter every Monday without fail, and before she knew it, it was November.

 _MUM!_

 _THERE WAS A_ _ **TROLL**_ _IN THE SCHOOL!_

 _I don't know how it got in, but the defense teacher came running into the great hall during the Halloween Feast screaming about there being a troll in the dungeons, then just fainted in the middle of the hall! Then everyone was screaming and panicking and Professor Dumbledore made these big bang noises with his wand and took the teachers to try and find the troll while the prefects got everyone back to their dorms. It was really scary, but I was safe, don't worry!_

 _Anyway, apparently this girl Hermione had been crying in the loos since lunchtime (I feel bad, but she is super annoying sometimes) and apparently it was Harry's friend Ron who had upset her, so Harry dragged Ron off to get Hermione as it was sort of his fault that she wasn't with the rest of us, and they ended up fighting the troll! They're all fine too, by the way, but they managed to knock it out with its own club, by levitating it and dropping it on its head! Is that cool or what?!_

 _Hope school is going okay for you!_

 _Love you lots,_

 _Eilidh_

 _Xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx_

No matter how 'cool' Eilidh found it, Isla was rather unimpressed. Schools were meant to be safe places, magic or not, and she made sure to send a rather scathing letter to Professor Dumbledore saying just that. She received a rather patronising and blasé letter in response, meant to reassure her that this was a one-time freak accident, and that nobody had been harmed, and that _of course_ they had now rectified the slight issue with the wards that had allowed the creature anywhere near the school.

Christmas that year felt, well, magical! Isla was so glad to have Eilidh home, and they spent most of the time chatting about all the cool things in the wizarding world. Isla was intrigued by potions, as it didn't seem to matter whether you had magic, at least for the stuff Eilidh had done in class so far. She was tempted to have a go herself, but was put off by Eilidh's stories of exploding cauldrons and foul smelling goop that got everywhere.

The rest of the year was pretty quiet as far as Isla was aware, although she did write another strongly worded letter when she found out that the defence teacher had died mysteriously at the end of the year. She was beginning to wonder exactly how safe the school was! Although, she mused, it was a magic school, so the normal rules didn't exactly apply.

Second year had a very expensive book list, and the guy on the cover looked like somebody Isla would have punched before she'd had Eilidh.

Eilidh was more subdued that year, and as she couldn't find a reason, Isla chalked it up to puberty. They did talk about how it was so cool that some people could talk to snakes though!

That year when Eilidh came home from school was one of the few times she had ever shouted at her daughter. Apparently, a huge murderous snake had been on the loose for the whole year and nearly killed several students, but Eilidh hadn't told her sooner because she didn't want to be pulled out of school. It was all okay now though as the snake had been killed and no serious harm was done. Or that was Eilidh's logic anyway.

They had a very long heart to heart that night. The upshot from it all was that Isla wrote yet another strongly worded letter about the events of the last two years, complete with three alternative plans of action that the school could have taken (after Isla had visited Diagon Alley and bought several books with detailed information about basilisks and the layout of hogwarts. Eilidh had also agreed not to keep such dangerous information secret from her mum, on the condition that Isla wouldn't immediately pull her out of Hogwarts without fully investigating the situation.

A few weeks later, the easy quiet of the O'Burn household was broken by a strangled cry of

"Oh _HELL_ no!"

 **A.N. I'm feeling relatively inspired at the moment, so am ploughing through this pretty quick. Next chapter we get to the good stuff :D**

 **Please do review :)**


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